Contribution of excited atoms to the index of refraction of a plasma

Abstract

The influence of excited atoms on the plasma refractive index is calculated for typical hydrogen arc plasma conditions. It is shown that the excited atoms contribution is, in many cases of interest, dominant in comparison with that of the ground state atoms, which is usually the only one taken into account. The effect on the total refractive index, including electrons and ions, strongly depends on the physical conditions and on the probe wavelength. At short wavelength and high pressures, the excited atoms can have a considerable influence.